This invention relates to a multiple system circular knitting machine for knitting stockings, said machine having a needle cylinder which can be driven either in a rotational or in a reciprocatory mode.
In a known machine of this type as described in DE-OS No. 28 25 864, the needles are always, i.e. not only in the reciprocating mode, but also in the rotation mode of the machine, advanced by means of jacks. Although this known machine is adapted to operate with three feeds in the reciprocating mode, so that the heel cup can be knit at high speeds, the machine has a rather low overall output, since the maximum obtainable speed in the rotation mode is limited by the necessity to move the jacks as well as the needles.
It has further been known for a long time to knit the heel portion on a four-feed circular knitting machine in the reciprocating mode employing only one feed. This method suffers from the disadvantage that the knitting speed of the machine is rather low in the reciprocating mode, so that the heel portion accounts for nearly a third of the overall time for the knitting of a stocking.
It is an object of the present invention to provide a multiple feed circular knitting machine of the type set forth in the introduction, which is capable of high operating speeds in the rotation mode as well as in the reciprocating mode.
This object is attained by a multiple system circular knitting machine for knitting stockings having leg portions and heel cup portions, said machine being operable in a rotation mode to knit said leg portions and being operable in a reciprocating mode to knit said heel cup portions, said machine comprising: needles, needle retractors (1-4), jacks (SCH) and jack advancing and retracting cams (13-30) together with narrowing (31-32) and widening (33-34) pickers, needle advancing cams (5-8) for advancing the needles in the rotation mode, and a reciprocating means for knitting the heel cup using at least two of said multiple systems; wherein during said reciprocating mode all needles are adapted to be retracted out of the knitting position by said needle retractors (1-4) and to be advanced only by means of said jacks (SCH), said needle advancing cams (5-8) being adapted to be deactivated in said reciprocating mode; so that said needles are lifted to their thread take-up position during said reciprocating mode solely by said jacks.
In the circular knitting machine according to the invention, the needle control in the rotation mode is carried out by needle cams without any contribution of the jacks, except for the case of pattern formation. In the rotation mode it is thus possible to achieve the maximum operating speed of which a circular knitting machine the needles of which are exclusively controlled by needle cams is capable. Since in the reciprocatory mode the needle advancing cams are deactivated, and the needles are solely raised by the jacks, it is possible, as in DE-OS No. 28 25 864, to knit the heel portion using two feeds without the danger of yarn breaks, so that a high operating speed is achieved also during formation of the heel portion. There is thus obtained a circular knitting machine including a reciprocatory operation mode for the production of stockings with a hitherto unobtained output rate.
In knitting of stocking heel portions in the reciprocating mode it is generally known that the needles have initially to be raised so far that the previously knit stitch slides over the tongue onto the needle shaft. Subsequently each needle is immediately pulled downwards into the tuck position, so that the freely exposed yarn adjacent the outermost needle cannot be caught under the tongue during knitting, which would otherwise result in dropped stitches and yarn breaks in the narrowing row. The downward movement of the needles to the tuck position is controlled by reversing cams.
In the known circular knitting machines having reciprocatory mode capability, the reversing cams are rigidly mounted in the cam support. In the rotation mode of the machine, the reversing cams accordingly also lower the previously advanced needles to the tuck position prior to their being fully withdrawn by the knitting cams. This results in difficulties at high rotational speeds, since the impingement of the needles on the reversing cams results in the occurrence of extremely high accelerations in the axial direction, which may lead to yarn breaks and needle damage.
It is therefore an additional object of the invention to improve a circular knitting machine in which reversing cams contribute to the needle control in the reciprocating mode in such a manner as to permit high rotational speeds in the rotation mode.
This additional object is attained by the knitting machine as described above and further including the feature that the reversing cam members (10, 11, 12) are adapted to be deactivated in said rotation mode.
In the rotation mode the reversing cams are thus deactivated, so that the needles are moved downwards solely by the knitting cams. This permits rotational speeds of up to about 800 rpm to be readily attained. A high production capacity is thus obtained in the rotation mode, with a similar capacity being maintained in the reciprocating mode due to the use of two systems.